Method and apparatus for scanning existing networks in TVWS

ABSTRACT

A method and an apparatus for scanning existing networks in TV White Space are disclosed. For scanning existing networks at a station to operate as an unlicensed device in a regulatory domain where a licensed device and the unlicensed device are permitted to operate, the method comprises: receiving a white space map (WSM) comprising information for available channels to be used for the unlicensed device to operate a wireless local area network (WLAN) operation and maximum transmission powers allowed for each of the available channels from an enabling station, wherein the enabling station is a station determining the available channels at its location using its own geographic location identification and a regulatory database access capability; and scanning the existing networks on the available channels identified within the received WSM.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims is a continuation of U.S. patent applicationSer. No. 12/908,449, filed on Oct. 20, 2010, which claims the benefit ofthe U.S. Provisional Application Nos. 61/313,129; 61/321,508;61/362,269;and 61/362,707, filed on Mar. 12, 2010; Apr. 7, 2010; Jul. 7,2010; and Jul. 9, 2010, respectively, which are hereby incorporated byreference as if fully set forth herein.

Application Ser. No. 12/908,449 also claims the benefit of Internationalpatent application Nos. PCT/KR 2009/006103 and PCT/KR 2009/006104, filedon Oct. 21, 2009, and Oct. 21, 2009, respectively, which are herebyincorporated by reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a wireless local area network (WLAN),and more particularly, to a method and apparatus for scanning existingnetworks in TV White Space.

Discussion of the Related Art

The standard for a Wireless Local Area Network (WLAN) technology isestablished by IEEE 802.11 standard association. IEEE 802.11a/b amongIEEE 802.11 standards provides 11 Mbps (IEEE 802.11b) or 54 Mbps (IEEE802.11a) transmission efficiency using unlicensed band on 2.4. GHz or 5GHz frequency band. IEEE 802.11g, adapting OFDM (Orthogonal FrequencyDivisional Multiplexing) technology, provides 54 Mbps transmissionefficiency. And, IEEE 802.11n, adapting MIMO-OFDM technology, provides300 Mbps transmission efficiency for 4 spatial streams. IEEE 802.11nprovides 40 MHz channel bandwidth, and in this case it provides up to600 Mbps transmission efficiency.

Now, a standard for regulating the WLAN operation in TV White Space isunder establishment, as IEEE 802.11af.

TV Whitespace includes channels allocated to broadcast TV, which arepermitted to be used by cognitive radio device. TV White Space mayinclude UHF band and VHF band. The spectrum not used by a licenseddevice (hereinafter, can be called as ‘White Space’) can be used by anunlicensed device. The frequency band permitted to be used by unlicenseddevice can be differently defined for each country. Generally, thisfrequency band comprises 54-698 MHz (US, Korea), and some of thisfrequency band can't be used for the unlicensed device. Here, ‘licenseddevice’ means a device of the user permitted in this frequency band, andcan be differently called as ‘primary user’, or ‘incumbent user’.Hereinafter, the term of ‘incumbent user’ can be collectively used forthese terms.

The unlicensed device, which wishes to use the TV White Space (TVWS),shall acquire information for available channel list at its location.Hereinafter, the unlicensed device operating in the TVWS using MAC(Medium Access Control) and PHY (Physical) operation according to IEEE802.11 can be called as TVWS terminal

Unlicensed device should provide a protection mechanism for theincumbent user. That is, the unlicensed device should stop using aspecific channel, when an incumbent user, such as wireless microphone,is using that specific channel. For this purpose, spectrum sensingmechanism is required. Spectrum sensing mechanism comprises EnergyDetection scheme, Feature Detection scheme, etc. By using thismechanism, unlicensed device determines that the channel is used by anincumbent user, when the strength of the primary signal is greater thana predetermined level, or when DTV (Digital Television) Preamble isdetected. And, the unlicensed device (station or Access Point) shalllower its transmission power, when it is detected that the neighboringchannel, next to the channel used by the unlicensed device, is used bythe incumbent user.

On the other hand, in order to efficiently operate the unlicensed deviceon TVWS, more discussion is needed on an enabling mechanism of lettingthe unlicensed device to operate in TVWS, how efficiently the unlicenseddevice finds the network to be connected, how the information for theavailable channel in TVWS is efficiently acquired, efficient format ofthat information, and efficient signaling mechanism to exchange thisinformation, etc.

SUMMARY OF THE INVENTION Technical Problem

One aspect of the present invention is for the enabling mechanism ofletting the unlicensed device to operate in TVWS in order to efficientlyoperate the unlicensed device on TVWS.

One example of this aspect is for providing a solution for the specificcase when dependent station receives enabling signal from a dependent APstation.

The other example of this aspect is for providing efficient way for anaccess point (AP) station to operate as a dependent station within TVWS.Another aspect of the present invention is for a mechanism that theunlicensed device efficiently finds the network to be connected.

Another aspect of the present information is for providing a mechanismto protect the incumbent user from the operation of the unlicenseddevice in TVWS.

Another aspect of the present information is for efficient format of theinformation for the available channel in TVWS.

The object of the present invention is not limited the above statedobjects, but includes various objects recited or apparent among thedetailed description of the present invention.

Technical Solution

One aspect of the present invention provides a method of scanningexisting networks at a station to operate as an unlicensed device in aregulatory domain where a licensed device and the unlicensed device arepermitted to operate, the method comprising: receiving a white space map(WSM) comprising information for available channels to be used for theunlicensed device to operate a wireless local area network (WLAN)operation and maximum transmission powers allowed for each of theavailable channels from an enabling station, wherein the enablingstation is a station determining the available channels at its locationusing its own geographic location identification and a regulatorydatabase access capability; and scanning the existing networks on theavailable channels identified within the received WSM.

In one example, the station scanning the existing networks may be adependent station, and the dependent station is a station receiving theinformation for the available channels from the enabling station or adependent AP (Access Point) station that enables the operation of thedependent station.

The station scanning the existing networks may operate only within theavailable channels identified by the WSM. And, the WSM may be receivedvia one of beacon frame, a probe response frame, and a white space mapannouncement frame.

In one example of the present invention, scanning the existing networkscan comprise: transmitting a probe request frame to a responding stationof a basic service set (BSS) on a specific channel among the availablechannels identified by the received WSM; and receiving a probe responseframe from the responding station on the specific channel. In this case,the responding station can be an AP station, and the probe responseframe can comprise the WSM.

In another example of the present invention, scanning the existingnetworks can comprise: listening a beacon frame from a station of abasic service set (BSS) on a specific channel among the availablechannels identified by the received WSM. In this case, the station ofthe BSS can be an AP station, and the beacon frame can comprise the WSM.

In one example of the present invention, the method may furthercomprises: receiving, at the dependent station, an updated WSM from theenabling station or the dependent AP station, wherein the dependentstation scan the existing networks on the available channels identifiedwithin the updated WSM.

Another aspect of the present invention provides an apparatus forscanning existing networks to operate as an unlicensed device in aregulatory domain where a licensed device and the unlicensed device arepermitted to operate, the apparatus comprising: a transceiver configuredto receive a white space map (WSM) comprising information for availablechannels to be used for the unlicensed device to operate a wirelesslocal area network (WLAN) operation and maximum transmission powersallowed for each of the available channels from an enabling station,wherein the enabling station is a station determining the availablechannels at its location using its own geographic locationidentification and a regulatory database access capability; and aprocessor configured to control scanning the existing networks on theavailable channels identified within the received WSM.

The apparatus can be configured to operate as a dependent station, wherethe dependent station is a station receiving the information for theavailable channels from the enabling station or a dependent AP (AccessPoint) station that enables the operation of the dependent station.

The processor may be configured to control the apparatus to operate onlywithin the available channels identified by the WSM.

In this aspect of the invention, the WSM may be received via one ofbeacon frame, a probe response frame, and a white space map announcementframe.

The processor may be configured to control the transceiver to transmit aprobe request frame to a responding station of a basic service set (BSS)on a specific channel among the available channels identified by thereceived WSM; and receive a probe response frame from the respondingstation on the specific channel. In this case, the responding stationcan be an AP station, and the probe response frame can comprise the WSM.

The processor may be configured to control the transceiver to listen abeacon frame from a station of a basic service set (BSS) on a specificchannel among the available channels identified by the received WSM. Inthis case, the station of the BSS can be an AP station, and the beaconframe can comprise the WSM.

The processor may be further configured to scan the existing networks onthe available channels identified within an updated WSM, when thetransceiver receives the updated WSM from the enabling station or thedependent AP station.

Advantageous Effect

According to one aspect of the present invention, effective enablingmechanism is provided.

Especially, it is more efficient to classify the unlicensed devices asan enabling station and a dependent station, where the enabling stationis a station determining the available channels at its location usingits own geographic location identification and a regulatory databaseaccess capability, while the dependent station is a station receivingthe available channel list from the enabling station or a dependent AP(Access Point) station that enables the operation of the dependentstation. It is because if all the unlicensed devices decide their ownenablement in TVWS, all of them have to have regulatory database accesscapability, and there shall be a signaling overhead. Further,specifically defining the operation of AP station as a first typedependent station which receives WSM from the enabling station as adependent station, but providing information for the second typedependent station, the system can be more effectively deployed. And, oneexample of the present invention provide a solution for the case whendependent station receives enabling signal from a dependent AP station.That is, by using transmitting/receiving the MAC address of the enablingstation during the DSE (Dynamic Station Enablement) procedure, thedependent station may know the MAC address of the enabling station evenwhen the enabling signal is received from a dependent AP station.

According to another aspect of the present invention, the unlicenseddevice can efficiently find the network to be connected, since it needsnot to scan all the channels. That is, by using the received WSMinformation, the scanning process can be limited to the allowablechannels identified by the received WSM. Therefore, scanning time can bereduced significantly.

According to another aspect of the present invention, the incumbent usercan be more effectively protected. That is, by using the measurementreport from a STA (e.g. DTV device) and by using the update mechanism ofthe WSM, the incumbent user can be more strongly protected.

According to another aspect of the present invention, efficient formatof the WSM is presented.

Various effects, not explicitly recited in this section, can be achievedby the present invention according to the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

In the drawings:

FIG. 1 shows an exemplary architecture of IEEE 802.11 system,

FIG. 2 is another exemplary architecture of IEEE 802.11 system in whichthe DS, DSM and AP components are added to the IEEE 802.11 architecturepicture,

FIG. 3 shows another exemplary architecture of IEEE 802.11 system forexplaining the concept of ESS,

FIG. 4 shows exemplary system architecture for better understanding theWLAN system,

FIG. 5 is a conceptual diagram to explain the enabling mechanismaccording to one embodiment of the present invention,

FIG. 6 shows an exemplary format of DSE Registered Location Element,

FIG. 7 shows an exemplary format of Registered Location element bodyfield,

FIG. 8 shows another example of the present invention regarding theaddress of the enabling STA,

FIG. 9 shows a newly defined DSE Registered location element body fieldaccording to one example of the present invention,

FIG. 10 shows an exemplary format of DSE Link identifier element of oneembodiment of the present invention,

FIG. 11 shows an exemplary DSE Enablement Frame format,

FIG. 12 shows channels defined in 2.4 GHz band for WLAN operation,

FIGS. 13 and 14 show examples for the channel granularity relationshipbetween TV channel and WLAN channel,

FIG. 15 shows a situation when a primary signal having a bandwidth lessthan 1 MHz is present,

FIG. 16 schematically shows the passive scanning scheme according to oneembodiment of the present invention,

FIG. 17 schematically shows the active scanning scheme according toanother embodiment of the present invention,

FIG. 18 shows an exemplary channel switch announcement informationelement structure,

FIG. 19 shows an exemplary channel occupancy information elementstructure,

FIG. 20 shows an exemplary Channel Occupancy Frame structure,

FIG. 21 shows a transmission mechanism of White Space Map announcementFrame between STAs according to one aspect of the present invention,

FIG. 22 shows an exemplary structure of WSM element according to oneembodiment of the present invention,

FIG. 23 shows one exemplary structure of TV Band WSM according to anembodiment of the present invention,

FIG. 24 shows an exemplary format of the Map ID bits,

FIG. 25 is an exemplary format of WSM information,

FIG. 26 shows an exemplary White Space Map Announcement Frame structureaccording to one embodiment of the present invention,

FIG. 27 is a schematic block diagram of wireless apparatusesimplementing an exemplary embodiment of the present invention,

FIG. 28 shows an exemplary structure of processor of STA apparatusaccording to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

Prior to describing the present invention, it should be noted that mostterms disclosed in the present invention correspond to general termswell known in the art, but some terms have been selected by theapplicant as necessary and will hereinafter be disclosed in thefollowing description of the present invention. Therefore, it ispreferable that the terms defined by the applicant be understood on thebasis of their meanings in the present invention.

For the convenience of description and better understanding of thepresent invention, general structures and devices well known in the artwill be omitted or be denoted by a block diagram or a flow chart.

First of all, Wireless Local Area Network (WLAN) system in whichembodiments of the present invention can be applied is explained.

FIG. 1 shows an exemplary architecture of IEEE 802.11 system.

The IEEE 802.11 architecture consists of several components thatinteract to provide a WLAN that supports STA (station) mobilitytransparently to upper layers. The basic service set (BSS) is the basicbuilding block of an IEEE 802.11 LAN. FIG. 1 shows two BSSs, each ofwhich has two STAs that are members of the BSS. It is useful to think ofthe ovals used to depict a BSS as the coverage area within which themember STAs of the BSS may remain in communication. (The concept ofarea, while not precise, is often good enough.) This area is called theBasic Service Area (BSA). If a STA moves out of its BSA, it can nolonger directly communicate with other STAs present in the BSA.

The independent BSS (IBSS) is the most basic type of IEEE 802.11 LAN. Aminimum IEEE 802.11 LAN may consist of only two STAs. Since the BSSsshown in FIG. 1 are simple and lack other components (contrast this withFIG. 2), the two can be taken to be represenative of two IBSSs. Thismode of operation is possible when IEEE 802.11 STAs are able tocommunicate directly. Because this type of IEEE 802.11 LAN is oftenformed without pre-planning, for only as long as the LAN is needed, thistype of operation is often referred to as an ad hoc network.

A STA's membership in a BSS is dynamic (STAs turn on, turn off, comewithin range, and go out of range). To become a member of a BSS, a STAjoins the BSS using the synchronization procedure. To access all theservices of an infrastructure BSS, a STA shall become “associated.”These associations are dynamic and involve the use of the distributionsystem service (DSS).

FIG. 2 is another exemplary architecture of IEEE 802.11 system in whichthe DS, DSM and AP components are added to the IEEE 802.11 architecturepicture.

PHY limitations determine the direct station-to-station distance thatmay be supported. For some networks, this distance is sufficient; forother networks, increased coverage is required. Instead of existingindependently, a BSS may also form a component of an extended form ofnetwork that is built with multiple BSSs. The architectural componentused to interconnect BSSs is the DS (Distribution System).

IEEE Std 802.11 logically separates the WM (wireless Medium) from thedistribution system medium (DSM). Each logical medium is used fordifferent purposes, by a different component of the architecture. TheIEEE 802.11 definitions neither preclude, nor demand, that the multiplemedia be either the same or different.

Recognizing that the multiple media are logically different is the keyto understanding the flexibility of the architecture. The IEEE 802.11LAN architecture is specified independently of the physicalcharacteristics of any specific implementation.

The DS enables mobile device support by providing the logical servicesnecessary to handle address to destination mapping and seamlessintegration of multiple BSSs.

An access point (AP) is any entity that has STA functionality andenables access to the DS, via the WM for associated STAs.

Data move between a BSS and the DS via an AP. Note that all APs are alsoSTAs; thus they are addressable entities. The addresses used by an APfor communication on the WM and on the DSM are not necessarily the same.

Data sent to the AP's STA address by one of the STAs associated with itare always received at the uncontrolled port for processing by the IEEE802.1X port access entity. In addition, if the controlled port isauthorized, these frames conceptually transit the DS.

Hereinafter, Extended Service Set (ESS) for a large coverage network isexplained.

FIG. 3 shows another exemplary architecture of IEEE 802.11 system forexplaining the concept of ESS.

The DS and BSSs allow IEEE Std 802.11 to create a wireless network ofarbitrary size and complexity. IEEE Std 802.11 refers to this type ofnetwork as the ESS network. An ESS is the union of the BSSs connected bya DS. The ESS does not include the DS. The key concept is that the ESSnetwork appears the same to an LLC (logical link control) layer as anIBSS network. STAs within an ESS may communicate and mobile STAs maymove from one BSS to another (within the same ESS) transparently to LLC.

Nothing is assumed by IEEE Std 802.11 about the relative physicallocations of the BSSs in FIG. 3. All of the following are possible:

The BSSs may partially overlap. This is commonly used to arrangecontiguous coverage within a physical volume.

The BSSs could be physically disjoint. Logically there is no limit tothe distance between BSSs.

The BSSs may be physically collocated. This may be done to provideredundancy.

One (or more) IBSS or ESS networks may be physically present in the samespace as one (or more) ESS networks. This may arise for a number ofreasons. Some examples are when an ad hoc network is operating in alocation that also has an ESS network, when physically overlapping IEEE802.11 networks have been set up by different organizations, and whentwo or more different access and security policies are needed in thesame location.

FIG. 4 shows exemplary system architecture for better understanding theWLAN system.

As can be understood, FIG. 4 is an example of infrastructure BSSincluding DS. And BSS 1 and BSS 2 consist of ESS. In WLAN system, a STAis a device operating according to MAC/PHY regulation of IEEE 802.11,and includes an AP STA and non-AP STA, such a laptop computer, mobilephone, etc. Usually, the device which a user directly handles is non-APSTA. Hereinafter, non-AP STA can be differently called as (terminal),WTRU (Wireless Transmit/Receive Unit), User Equipment (UE), MobileStation (MS), Mobile Terminal, Mobile Subscriber Unit, etc. And, non-APSTA, which can operate within TVWS spectrum, can be called as ‘Non-AP WSSTA’ or ‘WS STA’. AP can corresponds to Base Station (BS), Node-B,BTS(Base Transceiver System), or Femto BS in another field of wirelesscommunication. AP, which can operate within TVWS, can be called as WSAP.

Based on this understanding, the enabling mechanism of letting theunlicensed device to operate in TVWS according to one aspect of thepresent invention is explained.

In order for the unlicensed device to operate in TVWS, the unlicenseddevice should acquire information for available channels in TVWS notused by incumbent users. The most casual approach for this is definingsuch that all the unlicensed devices performs sensing whether there is aprimary signal of the incumbent user on each of the channels in TVWS.However, it may cost huge overhead, thus another approach can be using aregulatory database, such as TV band database which includes informationwhich of the channels are available for the WLAN operation at specificgeographic location. The present invention prefers to use the latterapproach.

Further, if all the unlicensed devices access the regulatory database toacquire information for the available channels, it may be inefficient,and produce large signaling overhead. Thus, embodiments of the presentinvention propose to classify the unlicensed devices (STAs) into anenabling STA, and a dependent STA. Enabling STA in TVWS is defined as aSTA determines the available TV channels at its location using its owngeographic location identification and TV bands database accesscapabilities. Dependent STA in TVWS is defined as a STA receivesavailable TV channel list from the enabling STA or the dependent AP ofthat enabling STA that enables its operation. Thus, according to theembodiment, enabling STA takes the role to permit the dependent STA tooperate within TVWS within the available channels (the role to enablethe dependent STA). This enabling procedure can be called as dynamicstation enablement (DSE) procedure.

FIG. 5 is a conceptual diagram to explain the enabling mechanismaccording to one embodiment of the present invention.

In FIG. 5, there is TVWS database, an enabling STA and a dependent STA.The enabling STA can be either an AP STA or non-AP STA. But, in anexample of FIG. 5, assume that the enabling STA is an AP enabling STA.

According to the embodiment, the enabling STA access the TVWS databasefor registration and querying channel information (S510). It is moreefficient for the enabling STA to acquire available channel list fromTVWS database than sensing each of the channels to determine whether itis available or not. Thus, the enabling STA of the present embodimentacquires the available channel list from TVWS database via Channel InfoResponse (S520).

Then, the enabling AP STA of this example may transmit beacon frame tothe dependent STA (S530) as an enabling signal to permit the dependentSTA to operate within TVWS. According to one embodiment of the presentinvention, this enabling signal comprises the beacon frame containing aDES Registered Location Element with ‘DSE RegLoc bit’ set to 1. Further,the present embodiment proposes the enabling STA to transmit informationfor the available channel list from TVWS. Hereinafter, the availablechannel list from TVWS can be called as White Space Map (WSM) or WSMelement. However, enabling STA can transmit enabling signal other thanthe TVWS. For example, the enabling STA can transmit beacon framecontaining a DES Registered Location Element with ‘DSE RegLoc bit’ setto 1 through 2.4 GHz band.

The dependent STA, according to the present embodiment, should operatewithin the available channels identified by the received WSM after itbecomes enabled. And, the dependent STA, according to the presentembodiment, may exchange DSE related message with the enabling STA. Morespecifically, the dependent STA may transmit DSE Enablement Requestmessage to the enabling STA for the enablement of the dependent STA(S540). Then, the enabling STA may respond to this request by DSEEnablement Response message (S550).

And, one embodiment of the present invention proposes that the enablingstation transmits the WSM after the transmission of a DSE Enablementframe (not shown in FIG. 5). It is efficient for the dependent stationto reduce scanning time for searching network to be connected.

FIG. 6 shows an exemplary format of DSE Registered Location Element, andFIG. 7 shows an exemplary format of Registered Location element bodyfield.

As stated above, DSE Registered Location element (FIG. 6) with RegLocDSE bit (FIG. 7) set to 1 can be an enabling signal permitting thedependent STA to operate WLAN operation in TVWS. The dependent STA,receiving and decoding the DSE Registered Location element, may transmitEnablement Request Frame to the Enabling STA. The dependent STA shalltransmit the Enablement Request Frame on a channel identified by‘Channel Number’ field of Registered Location element body, as shown inFIG. 7. This channel identified by ‘Channel Number’ field of RegisteredLocation element body can be located other than TVWS, or within TVWSamong the available channels identified by WSM. Then, the enabling STAtransmits Enablement Response Frame to the dependent STA, and if thedependent STA receives it, the DSE procedure is completed.

On the other hand, dependent STA according to IEEE 802.11y shouldreceive the enabling signal from the enabling STA over-the-air. However,this requirement is not necessarily applied to TV White Space.Therefore, the dependent AP also can transmit the enabling signal bytransmitting beacon frame, probe response frame including DSE RegisteredLocation element.

FIG. 8 shows another example of the present invention regarding theaddress of the enabling STA.

The DSE procedure between the enabling STA and the dependent AP STA isthe same as shown in FIG. 5. As stated above, dependent AP receives theenabling signal (DSE Registered Location element with DSE RegLoc bit setto 1) and WSM from enabling STA, transmits DSE Enablement requestmessage, receives DSE Enablement response message, and then enabled.

In this example, the dependent AP STA also can transmit enable signal(DSE Registered Location element with DSE RegLoc bit set to 1) to thedependent STA (S410). Here, dependent AP may transmit beacon frameincluding DSE Registered Location element through non-TVWS Link.

Dependent AP of the present embodiment shall inform the dependent STAthat this DSE Registered Location element is transmitted by thedependent AP. Thus, Reserved Bit (B126) of DSE Registered Locationelement (FIG. 7) can be used as ‘Dependent AP indication bit’.

FIG. 9 shows a newly defined DSE Registered location element body fieldaccording to one example of the present invention. As shown in FIG. 5,the newly defined DSE Registered location element includes Dependent APbit.

Table 1 shows the values of Dependent STA bit and Dependent AP bitaccording to the subject of transmitting DSE Registered locationelement.

TABLE 1 Dependent STA bit value Dependent AP bit value Enabling STAFalse False Dependent AP True True Dependent STA True False

As shown in Table 1, Dependent AP bit is used to identify Dependent APfrom Dependent STA. That is, dependent STA receiving DSE Registeredlocation element can be informed whether the DSE Registered locationelement it transmitted from the dependent AP STA or enabling STA basedon the values of Dependent STA bit and Dependent AP bit.

On the other hand, the DSE Registered location element may only includethe transmitter's address in it. Thus, if the dependent STA receives theenabling signal from the dependent AP, the dependent STA can't know theaddress of the enabling signal. In this case, the dependent STA can'ttransmit the DSE Enablement Request to the enabling STA. Therefore, oneembodiment of the present invention proposes for the dependent AP STA totransmit a DSE Link identifier element including MAC address of theenabling STA during the DSE procedure.

FIG. 10 shows an exemplary format of DSE Link identifier element of oneembodiment of the present invention.

In (a) of FIG. 10, the Element ID field is equal to the DSE LinkIdentifier value. The Length field may be set to 12. TheResponderSTAAddress field is the MAC address of the enablement responderSTA that grants enablement (enabling STA). The length of the

ResponderSTAAddress field may be 6 octets.

The BSSID field may set to the BSSID of the BSS to which the enablementresponder STA is associated. When the DSE enablement messages areexchanged over the air, the dependent STA should know the BSSIDassociated with the enabling STA. Thus, When the DSE enablement messagesare not exchanged over the air, the BSSID field may not be present.

In (b) of FIG. 10, DSE Link identifier element may further includesenabling STA timestamp field for time synchronization among enablingSTA, dependent AP and dependent STA associated to the corresponding AP.

Referring back to FIG. 8, dependent AP transmits DSE Link identifierelement to the dependent STA (S420). By using this, the dependent STAcan acquire the MAC address of the enabling STA. Thus, the dependent STAmay transmit DSE Enablement frame to the enabling STA for the enablement(S430). Here, the dependent STA transmits DSE Enablement frame on achannel identified by ‘Channel Number’ field of Registered Locationelement body received from the dependent AP.

Further, according to another embodiment of the present invention, thedependent STA may broadcast DSE identifier element including the addressof the enabling STA. When, the dependent STA is AP STA, this DSEIdentifier element can be transmitted via beacon frame or probe responseframe.

FIG. 11 shows an exemplary DSE Enablement Frame format.

When DSE Enablement Frame format of FIG. 11 is DSE Enablement frame forDSE Enablement Request, RequesterSTAAddress field indicates MAC addressof STA transmitting this DSE Enablement Frame, and ResponderSTAAddressfield indicates MAC address of STA receiving this DSE Enablement Frame.Reason Result Code field may indicates whether this DSE Enablement Frameis for DSE Enablement Request, or DSE Enablement Response. Enablementidentifier field may indicate enablement ID allocated by the enablingSTA to the dependent STA, when DSE Enablement Frame is for DSEEnablement Response.

Thus, RequesterSTAAddress field of the DSE Enablement frame for DSEEnablement request transmitted by dependent STA indicates the MACaddress of the dependent STA, and ResponderSTAAddress field indicatesthe MAC address of the enabling STA, and Reason Result Code fieldindicates this DSE Enablement Frame is for DSE Enablement Request. And,Enablement identifier field is set to invalid value.

Address 3 field of MAC header of DSE Enablement Request frame is set toBSSID field of DSE Link Identifier element, ResponderSTAAddress field ofDSE Enablement Request frame is set to MAC address of the enabling STAreceiving DSE Enablement Request frame via DSE Link Identifier element.

As shown in FIG. 8, enabling STA receiving the DSE Enablement Requestframe transmits DSE enablement frame for DSE Enablement Response (S440).Here, Enabling STA may allocate (Dependent) Enablement Identifier of 16bits to the dependent STA.

When DSE Enablement Frame format of FIG. 11 is for DSE EnablementResponse, the RequesterSTAAddress field of the DSE Enablement frame forDSE Enablement Response indicates the MAC address of the enabling STA,ResponderSTAAddress field indicates the MAC address of the DependentSTA, Reason Result Code field indicates that the DSE Enablement frame isfor DSE Enablement Response. And, Enablement identifier field mayinclude Enablement ID allocated to the dependent STA by the enablingSTA.

In brief, embodiments of the present invention propose to classify theunlicensed devices (STAs) into an enabling STA, and a dependent STA.Enabling STA in TVWS is defined as a STA determines the available TVchannels at its location using its own geographic locationidentification and TV bands database access capabilities. Dependent STAin TVWS is defined as a STA receives available TV channel list from theenabling STA or the dependent AP of that enabling STA that enables itsoperation. Thus, according to the embodiment, enabling STA has anauthority to permit the dependent STA to operate within TVWS within theavailable channels (the role to enable the dependent STA). This enablingprocedure can be called as dynamic station enablement (DSE) procedure.

Hereinafter, another aspect of the present invention for a mechanismthat the unlicensed device efficiently finds the network to be connectedis disclosed. This aspect of the present invention is related to how theinformation for the available channel in TVWS is efficiently acquired.

In order to operate in TVWS as an unlicensed device, a STA should findthe network to be connected. This type of process may be called as‘scanning’. If we assume that the channel bandwidth used for by the IEEE802.11 TVWS protocol in TVWS is the same as the channel bandwidth usedby Digital TV (DTV), the channel bandwidth of each channel shall be 6MHz. For IEEE 802.11 operation in 2.4 GHz and 5 GHz, the channelbandwidth is 20 MHz. This means that there are a lot more channels to bescanned by a STA in TVWS than the channels in 2.4 GHz and/or 5 GHz. Thiscan significantly increase the scanning time and power consumption for aSTA to find the network to be connected.

Also, in order to operate in TVWS as an unlicensed device, a STA shouldhave a mechanism for protecting the incumbent user. The most casualapproach to find the available channel in TVWS is performing, at theSTA, ‘sensing’ to find whether there is an incumbent user operates on aspecific channel. (It should be noted that the term ‘sensing’ is forfinding whether there is a primary signal on a specific channel, thatis, for finding the available channel, while the term ‘scanning’ is forfinding the network to be connected.) Another approach is accessing theexternal regulatory domain database (DB) to find the available channellist in TVWS. For the TVWS, the external regulatory DB can be TV banddatabase. The DB can include information for scheduling of licensedusers at a specific geographic location. Therefore, one embodiment ofthe present invention proposes the enabling STA to access via internetto the regulatory domain database and acquire the available channel listat its own geographic location, and to deliver this available channellists to other STAs, rather than each of the STAs perform sensing everychannels to find whether they are available or not. In this document,information for the available channel list from the regulatory domaindatabase may be called as ‘White Space Map (WSM)’ Further, if a STAacquires the available channel list in TVWS to operate, the STA need notperform scanning on a channel identified as not available by WSM.Therefore, acquiring the WSM from DB and delivering this WSM canefficiently reduce the scanning time and power consumption.

Here, one embodiment of the present invention proposes the WSMindicating the list of available channels with the first channelgranularity, while the second channel granularity is used for the WLANoperation. This is explained with regards to FIGS. 12 -15.

FIG. 12 shows channels defined in 2.4 GHz band for WLAN operation.

As shown in FIG. 12, there are 14 channels for WLAN operation in 2.4 GHzband. Each of the channels has center frequency at 2.412, 2.417, 2.422,. . . , 2.472 GHz. And, orthogonal channels which do not overlap eachother are used for WLAN operation. In FIG. 12, channels 1, 6 and 11 canbe used for WLAN operation. FIG. 12 shows each channel span over 22 MHz,however it is actually 20 MHz used for WLAN operation. (20 MHz channelgranularity)

Depending on the country, the channels used for WLAN operation can bedifferent. For example, channels 1-11 are used for WLAN operation inNorth America. Example shown in FIG. 12 is for 20 MHz channelgranularity for WLAN operation. However, IEEE 802.11 PHY can use 5, 10,20 and 40 MHz granularity using deferent sample rates.

FIGS. 13 and 14 show examples for the channel granularity relationshipbetween TV channel and WLAN channel.

As stated above, TV band database has available channel information with6 MHz TV channel. Thus, if the WSM is designed to indicate availablechannel with 5 MHz (or 10/20/40 MHz) for WLAN operation, it may cost tomodify the information already in the TV band database. Therefore, oneexample of the present invention propose the WSM indicating available TVchannels with 6 MHz channel granularity, and the WLAN STA receiving theWSM and operating as an unlicensed device operates using 5 MHz (or10/20/40 MHz) channel granularity. FIGS. 13 and 14 show an examples for5 MHz and 20 MHz channel granularities for WLAN operation, while the WSMindicates the available TV channels.

Further, even when we modifies the channel granularity from the TV banddatabase, it is not efficient to design available channels withgranularity of 5/10/20/40 MHz. Rather, one example of the presentinvention proposes to use smaller channel granularity, such as 1 MHz,for the WSM. FIG. 15 shows the benefit of this example.

There is a situation when a primary signal having a bandwidth less than1 MHz (for example, microphone signal) is present as shown in FIG. 15.In this case, the whole of 6 MHz TV channel within which the primarysignal is detected can be treated as unavailable. This can waist thefrequency resource. However, if the WSM indicates available channel with1 MHz channel granularity, 5 MHz WLAN channel can be established asshown in FIG. 15, thus, according to this example, we can efficientlyuse the available frequency resource.

In another example of the present invention propose the WSM to indicatechannels which are not available, instead of indicating availablechannels. When there are fewer channels which are not available for WLANoperation, it is more efficient to indicate unavailable channels,instead of available channels.

Based on this, the scanning process according to one aspect of thepresent invention will be disclosed. In IEEE 802.11, there are two typesof scanning process. One is a passive scanning process, and the other isan active scanning process. Two types of scanning processes according toone aspect of the present invention are explained.

FIG. 16 schematically shows the passive scanning scheme according to oneembodiment of the present invention.

In the passive scanning scheme, the scanning STA waits for a beaconframe while moving each channel on a channel list. The channel listspecifies a list of channels that are examined when scanning for a BSS.In present embodiment, the list of channels is restricted to theavailable channel list identified by WSM to reduce the scanning time.

The beacon frame, one of management frames in IEEE 802.11, isperiodically transmitted to inform about the presence of a wirelessnetwork, allow the scanning STA to search for the wireless network tojoin it. In an infrastructure network, an access point (AP) serves toperiodically transmit the beacon frame.

When the scanning STA receives the beacon frame, it buffers the beaconframe to acquire information about a BSS, and records the beacon frameinformation in each channel while moving channels within the availablechannels identified by the received or acquired WSM.

With reference to FIG. 16, assume that a scanning STA 220 is a laptopcomputer equipped with IEEE 802.11 communication module. Also, assumethat the scanning STA 220 operates as a dependent STA, which was enabledand receives WSM comprising available channel list in TVWS from anenabling STA or an AP.

A scanning STA 220 performs channel scanning in a particular channelwithin the available channels according to the passive scanning scheme.If the scanning STA 220 receives a beacon frame 215 transmitted by anAP1 210 of a BSS1 and a beacon frame 225 transmitted by an AP2 220 of aBSS2, but not a beacon frame 235 transmitted by an AP3 230 of a BSS3,the scanning STA 220 performs buffering that the two BSSs (BSS1 andBSS2) have been discovered from a current channel and moves to anotherchannel. Repeatedly performing this process, the scanning STA 220performs scanning on every channel within the available channels. Since,the scanning STA 220 needs not to perform scanning on channelsidentified as not available by WSM, the scanning time can be reducedsignificantly.

FIG. 17 schematically shows the active scanning scheme according toanother embodiment of the present invention.

In the active scanning scheme, the scanning STA transmits a proberequest frame, a management frame, transmitted to probe into an APpresent nearby while moving each channel on the channel list, and waitsfor a pertinent response. In present embodiment, the channel list isrestricted to the available channel list identified by WSM to reduce thescanning time.

In response to the probe request frame, a responder transmits a proberesponse frame to the scanning STA. Here, the responder refers to an STAwhich has finally transmitted a beacon frame in a BSS of a channel whichwas being scanned. In an infrastructure BSS, an AP transmits a beaconframe, so the AP is the responder, while in an IBSS, STAs within theIBSS transmits a beacon frame by turns, so a responder is not fixed.

With reference to FIG. 17, assume that a scanning STA 300 is a laptopcomputer equipped with IEEE 802.11 communication module. Also, assumethat the scanning STA 300 operates as a dependent STA, which was enabledand receives WSM comprising available channel list in TVWS from anenabling STA or an AP.

When a scanning STA 300 transmits a probe request frame 305, a firstresponder 310 of the BSS1 and a second responder 320 of the BSS2, whichhave listened to it, unicast a first probe response frame 315 and asecond probe response frame 325 to the scanning STA 300, respectively.Upon receiving the first and second probe response frames 315 and 325,the scanning STA 300 buffers BSS-related information from the receivedprobe response frames, moves to a next channel, and performs scanning onthe next channel in the same manner. As stated above, since the scanningSTA 300 needs not to perform scanning on channels identified as notavailable by WSM, the scanning time can be reduced significantly. Theprobe response frame may further comprise AP's capability informationelement, HT operation element, EDCA parameter set element, etc.

In summary, one aspect of the present invention proposes the enablingSTA to transmit the available channel list in TVWS as WSM to dependentSTA(s) via beacon frame or Probe Response frame to reduce the scanningtime of the dependent STA. The transmission of WSM can be both periodicand event-triggered.

Further, one embodiment of the present invention proposes that when aSTA, receiving WSM, tries to scan AP using available channel list inWSM, the STA does not scan WLAN channel in which whole or part of the TVchannel thereof is identified as not available. That is, as explainedabove, the STA(s) shall operate with first channel granularity (WLANchannel granularity) while the WSM indicates available channel withsecond channel granularity (available TV channels). Thus, even when apart of one WLAN channel includes TV channel which is not available,that WLAN channel can't be used.

The detailed structure of WSM element and transmission of WSM will bedisclosed later. Before this, a mechanism to protect the incumbent user(e.g. DTV) from the operation of the unlicensed device in TVWS accordingto one aspect of the present invention will be disclosed.

As stated above, the unlicensed device including WS STA should provide aprotection mechanism for the incumbent user. That is, if a specificchannel is used by an incumbent user, such as wireless microphone, theunlicensed device should stop using this channel. For that purpose, theunlicensed device can perform spectrum sensing to find whether aspecific channel is used by a primary user. Spectrum sensing mechanism,which can be used, includes Energy Detection scheme, Feature Detectionscheme, etc.

If the unlicensed device finds that the strength of the primary signalis higher than a predetermined level, or if the unlicensed devicedetects the DTV preamble, the unlicensed device may determine that thatchannel is used by an incumbent user. And, if the unlicensed devicedetermines on a specific channel that the neighboring channel next tothe specific channel is used by the incumbent user, the unlicenseddevice should lower its transmission power to protect the incumbentuser. Therefore, WSM element, according to one embodiment of the presentinvention, comprises maximum allowed power level information for each ofthe available channels in WSM.

One embodiment of the present invention is for providing protectionmechanism for DTV operating as a primary user in TVWS by sharing theinformation from the TV sensing of DTV in TVWS with TV band database(TVDB). Specifically, this embodiment proposes using the informationcollected by DTV in TVWS, because DTV has tuner which can performsensing TVWS channels, thus DTV can know the channels occupied by DTVbroadcasting without accessing TVDB. Further, DTV also can be a TV banddevice (TVBD) operating in TVWS, thus it can report/broadcast the resultof its sensing.

When DTV operates in TVWS, it be more probable that DTV operates as WSSTA than as WS AP. Thus, the present embodiment proposes DTV operatingas WS STA to report the channel sensing result or measurement report toWS AP, when it processes association with WS AP. By this, WS AP canacquire which of the channels are used for TV broadcasting withoutaccessing TVDB. Even when WS AP has information regarding channels usedfor broadcasting and/or broadcasting schedule, the WS AP can correctlyrespond to the mismatch between its own WSM and the report from STA(DTV).

More specifically, DTV(Digital TV), operating as non-AP STA in general,may transmit a channel sensing result frame indicating which of thechannels are used for TV broadcasting to AP STA. Then, WS AP shouldcompare this report with WSM acquired from DB access. If there is achannel identified as available by WSM, but this channel is used orscheduled to be used for TV broadcasting, the unlicensed device shouldnot operate on that channel. And, it may update WSM when it receives ameasurement report in which a primary service signal is measured on achannel, which is indicated as from the regulatory domain databasesystem.

This mechanism can be used as protection mechanism to protect DTV. Whena specific DTV device operates on a specific channel for receiving TVbroadcasting signals, and if it detects other WS STA/WS AP operates onthat specific channel (if it detects IEEE 802.11af preamble), the DTVdevice can report/broadcast channel sensing result. And/or, the DTVdevice may transmit signals asking WS STA/WS AP to stop using thatchannel. Then, WS STA/WS AP should stop using that channel, and move toanother channel.

One example of signals asking WS STA/WS AP to stop using a specificchannel is using channel switch announcement information element.

FIG. 18 shows an exemplary channel switch announcement informationelement structure.

Element ID field may indicates that the present information element (IE)is channel switch announcement information element. Length field mayindicate the length of the present IE. Channel Switch Mode field mayindicate switching mode of 802.11af STA.

And, when new channel number field of the IE is set to a specific value(e.g, 11111111, 00000000), it can be treated as asking to stop using thepresent channel. Here, channel switch count is supposed to be set asasking to stop using this channel immediately.

Another example of signals asking WS STA/WS AP to stop using a specificchannel is defining and using channel occupancy information element.

FIG. 19 shows an exemplary channel occupancy information elementstructure.

Element ID field may indicate that the present IE is channel occupancyIE. Length field may indicate the amount of information contained inthis IE. The channel number in FIG. 19 may indicate the channel numberdetermined as used by WS STA/WS AP while that channel is used by DTV. Ifthere are multiple channels determined as used by WS STA/WS AP whileused by DTV, each channel number of these channels can be included.Thus, the length of this IE is variable.

FIG. 20 shows an exemplary Channel Occupancy Frame structure.

Channel occupancy frame of FIG. 20 is for transmitting channel switchannouncement information element of FIG. 18. However, so long as DTV,operating as primary user in TVWS, can protect its operation in TVWS byits measurement report, any frame which can be transmitted to enablingSTA including any IE including channel occupancy information element ofFIG. 19 can be used.

The above explained mechanism for protecting the incumbent user can beapplied to other primary user devices, having sensing ability, otherthan DTV device.

As stated above, enabling STA shall update WSM, when there is a mismatchbetween the WSM from DB access and the report from any other STA, andwhen there is a channel identified as available by WSM, but this channelis used or scheduled to be used for TV broadcasting. And, one embodimentof the present invention proposes the enabling STA to transmit theupdated WSM to dependent STA(s), whenever the information from theregulatory domain database is updated, and the enabling STA retrievesthe updated available channel information from the DB. The enabling STAcan transmit the updated WSM via the above explained beacon frame orprobe response frame.

When the enabling STA is non-AP STA, the enabling STA is proposed totransmit the updated WSM via White Space Map Announcement Frame whichwill be explained below.

FIG. 21 shows a transmission mechanism of White Space Map announcementFrame between STAs according to one aspect of the present invention.

In FIG. 21, when STA A transmits White Space Map Announcement frame toSTA B to transmit the updated WSM, STA A can be an enabling STA and STAB can be a dependent STA. STA A and STA B may comprise SME(StationManagement Entity) and MLME(MAC Layer Management Entity). First, SME ofSTA A SME may transmit MLME-WSM.request to MLME of STA A. This primitiveis for requesting to transmit White Space Map announcement frame toother STA. The MLME-WSM.request may comprise MAC address of STA B and(updated) WSM. MLME of STA A, receiving the MLME-WSM.request, maygenerate White Space Map announcement frame, and transmit it to MLME ofSTA B. In this example, the White Space Map Announcement frame generatedby MLME of STA A comprises (updated) WSM.

MLME of STA B, receiving White Space Map announcement frame comprising(updated) WSM from MLME of STA A, may indicate this to SME usingMLME-WSM.indication. MLME-WSM.indication primitive may comprise MACaddress of STA A and (updated) WSM. For the example for WSM update,where enabling STA as non-AP STA updates WSM, STA A is non-AP STA, thusMLME-WSM.indication may comprise address of non-AP STA MAC entity. SMEof STA B, receiving MLME-WSM.indication, controls STA B to operate onlywithin the available channels identified by the received WSM.

In summary, the enabling STA can transmit (updated) WSM to a dependentSTA via at least one of beacon frame, probe response frame, and WhiteSpace Map Announcement frame. When the enabling STA is non-AP STA, theenabling STA may transmit (updated) WSM via White Space Map Announcementframe.

Hereinafter, operation of AP STA as dependent STA is explained.

As explained above, AP STA can be a dependent STA receiving the WSM froman enabling STA. However, the dependent AP STA, according to oneembodiment of the present invention, also plays a role for forwardingthe received WSM within at least one beacon frame in every beacontransmission instances with a predetermined transmission interval foranother dependent STA. Thus, the dependent AT STA can be called as thefirst type dependent STA while another dependent STA receiving the WSMfrom the dependent AP STA can be called as the second type dependentSTA. Further, when the dependent AP STA receives an updated WSM from anenabling STA, it should operate only within the available channelsidentified by the updated WSM, since the dependent AP STA is also adependent STA (the first type dependent STA) operating as an unlicenseddevice in TVWS. That is, if the dependent AP STA is operating on achannel which becomes unavailable by the updated WSM, the dependent APSTA should move to another channel identified as available according tothe updated WSM. Further, the dependent AP STA, according to the presentexample, shall transmit the updated WSM in a next beacon transmissioninstance when the WSM is supposed to be transmitted within the beaconframe.

In this example for the dependent AP STA, if the AP STA receives a proberequest frame on a specific channel identified by the WSM from thedependent STA (the second type dependent STA), the AP STA shall transmita probe response frame comprising the WSM to the dependent STA (thesecond type dependent STA).

Hereinafter, WSM structure according to one aspect of the presentinvention will be explained.

FIG. 22 shows an exemplary structure of WSM element according to oneembodiment of the present invention.

WSM element comprises available channel list from the regulatorydatabase. Further, as stated above, when the unlicensed device operateson a specific channel which is available in TVWS and the neighboringchannel next to the specific channel is used by an incumbent user, theunlicensed device should lower its transmission power to protect theincumbent user. Therefore, one embodiment of the present inventionproposes WSM element comprising available channel list and maximumallowed transmission power of the available channels from the regulatorydatabase. Further, as stated above, available channels identified by theWSM can have a first channel granularity, while STAs operating in TVWSuse channels having a second channel granularity. Preferably, the WSMelement may indicate available TV channels, but channel granularity canbe differently set as stated above. In another example of the presentinvention, the WSM element can indicate unavailable channels instead ofavailable channels, as stated above.

Actual maximum of transmission power level may be decided depending onthe channel bandwidth and the maximum allowed transmission powers peravailable channel. When the operational channel bandwidth (WLAN channel)spans multiple channels indicated in the WSM, whose maximum power levelsare different, the operational transmission power level shall beconstrained by the minimum transmission power level of those multiplechannels, which are indicated in the WSM.

Preferably, as shown in FIG. 22, WSM element may comprise Element IDfield, Length field, WSM Type field and WSM Information field.

Element ID field may indicate that this element is White Space Mapelement. Length field has a variable value in a unit of octetcorresponding to the length of WSM. Since the numbers of availablechannels and corresponding maximum power level values are variable, thelength field may indicate the length of WSM element.

WSM type field may indicate the type of WSM information. Specifically,WSM type may indicate whether WSM information is TV Band WSM, or othertype of WSM. If WSM type indicates that the present WSM element is TVBand WSM element, this WSM element is a WSM element including theavailable channel list and the maximum transmission powers allowed foreach of the available channels, which was acquired from TV band databaseby the enabling STA.

According to one example of the present invention, the information in aWSM element is valid for a ‘dot11WhiteSpaceMapValidTime’ from thetransmission of the beacon frame containing WSM element. The value of‘dot11WhiteSpaceMapValidTime’ may be predetermined between STAs/APs. Ifthe WSM is invalid, APs are preferred not to transmit a WSM element andpreferred not to transmit any signal in the regulatory bands anddependent STAs become unenabled. If an enabled dependent STA does notreceive a WSM within dot11WhiteSpaceMapValidTime, it becomes unenabled.Here, “unenabled” means STA does not operate in TVWS.

FIG. 23 shows one exemplary structure of TV Band WSM according to anembodiment of the present invention.

As shown in FIG. 23, TV Band WSM may comprise MAP ID field, ChannelNumber field, Maximum Power Level field.

Map ID field is an identifier of the TV band WSM information fieldformat for a TV band WSM and the format of the Map ID bits isillustrated in FIG. 24.

Referring to FIG. 24, type bit is one bit in length and indicateswhether the following channel list is a full channel list or a partialchannel list. If the Type bit is set to 1, the following channel list isa full channel list and if the Type bit is set to 0, the followingchannel list is a partial channel list.

Map version of FIG. 24 may be 6 bits in length and identifies theversion of WSM. When the available channel information from the TV banddatabase is updated and the corresponding WSM is updated, then the Mapversion is circularly incremented by 1 and the default bit value of theMap version is 0000000.

If a STA receives several WSMs with the same Map version and the Typebit is set to 0 (partial WSM), the STA shall construct the whole channellist using the multiple WSMs having the same Map version.

Now, referring back to FIG. 23, the Channel Number field may be apositive integer value that indicates where the TV channel is availablefor WLAN operation. The length of the Channel Number field may be set as1 octet. When the Channel Number and Maximum Power Level pairs arerepeated (as indicated in FIG. 23), they shall be listed in increasingTV channel numbers. FIG. 25 is an exemplary format of WSM information.

Hereinafter, White Space Map Announcement Frame structure according toone example of the present invention is explained.

FIG. 26 shows an exemplary White Space Map Announcement Frame structureaccording to one embodiment of the present invention.

The White Space Map Announcement frame may use the Action frame bodyformat as shown in FIG. 26. The Category field may be set to the valuefor predefined public action defined. The Action field may be set to thevalue indicating White Space Map Announcement frame. The remainingfields are as defined in the White Space Map element body explainedabove.

FIG. 27 is a schematic block diagram of wireless apparatusesimplementing an exemplary embodiment of the present invention.

An AP 700 can include a processor 710, a memory 720, a transceiver 730,and a STA 750 may include a processor 760, a memory 770, and atransceiver 780. The transceivers 730 and 780 transmit/receive a radiosignal and implement an IEEE 802 physical layer. The processors 710 and760 are connected with the transceivers 730 and 760 to implement an IEEE802 physical layer and/or MAC layer. The processors 710 and 760 mayimplement the above-described channel scanning method.

The processors 710 and 760 and/or the transceivers 730 and 780 mayinclude an application-specific integrated circuit (ASIC), a differentchip set, a logical circuit, and/or a data processing unit. The memories720 and 770 may include a read-only memory (ROM), a random access memory(RAM), a flash memory, a memory card, a storage medium, and/or any otherstorage units. When an exemplary embodiment is implemented by software,the above-described scheme may be implemented as a module (process,function, etc.) performing the above-described functions. The module maybe stored in the memories 720 and 770 and executed by the processors 710and 760. The memories 720 and 770 may be disposed within or outside theprocessors 710 and 760 and connected with the processors 710 and 760 viawell-known means.

Among these elements of apparatuses for AP/STA, the structure ofprocessor 710 or 760 will be more specifically explained.

FIG. 28 shows an exemplary structure of processor of STA apparatusaccording to one embodiment of the present invention.

Processor 710 or 760 of STA may have multiple layer structures, and FIG.28 especially focuses on MAC sublayer (1410) on data link layer (DLL)and Physical layer (1420) among these layers. As shown in FIG. 28, PHY(1420) may include PLCP entity (physical layer convergence procedureentity; 1421) and PMD entity (physical medium dependent entity; 1422).Both the MAC sublayer (1410) and PHY (1420) conceptually includemanagement entities, called MLME (MAC sublayer Management Entity; 1411)and PLME (physical layer management entity; 1421), respectively. Theseentities (1411, 1421) provide the layer management service interfacesthrough which layer management functions can be invoked.

In order to provide correct MAC operation, an SME (Station ManagementEntity; 1430) is present within each STA. The SME (1430) is a layerindependent entity that can be viewed as residing in a separatemanagement plane or as residing “off to the side.” The exact functionsof the SME (1430) are not specified in this document, but in generalthis entity (1430) can be viewed as being responsible for such functionsas the gathering of layer-dependent status from the various layermanagement entities (LMEs), and similarly setting the value oflayer-specific parameters. SME (1430) would typically perform suchfunctions on behalf of general system management entities and wouldimplement standard management protocols.

The various entities within FIG. 28 interact in various ways. FIG. 28shows some examples of exchanging GET/SET primitives. XX-GET.requestprimitive is used for requesting the value of the given MlBattribute(management information base attribute). XX-GET.confirm primitive isused for returning the appropriate MIB attribute value ifstatus=“success,” otherwise returning an error indication in the Statusfield. XX-SET.request primitive is used for requesting that theindicated MIB attribute be set to the given value. If this MIB attributeimplies a specific action, then this requests that the action beperformed. And, XX-SET.confirm primitive is used such that, ifstatus=“success,” this confirms that the indicated MIB attribute was setto the requested value, otherwise it returns an error condition instatus field. If this MIB attribute implies a specific action, then thisconfirms that the action was performed.

As shown in FIG. 28, MLME (1411) and SME (1430) may exchange variousMLME GET/SET primitives via MLME_SAP (1450). According to one example ofthe present invention, SME (1430) may transmit MLME_WSM.requestprimitive to MLME (1411) for requesting MLME (1411) to transmit theWhite Space Map Announcement Frame to another STA. In other case, MLME(1411) may transmit MLME-WSM.indication primitive to SME (1430) toindicate the reception of the White Space Map Announcement Frame fromanother STA.

Also, as shown in FIG. 28, various PLCM_GET/SET primitives may beexchanged between PLME (1421) and SME (1430) via PLME_SAP (1460), andbetween MLME (1411) and PLME (1470) via MLME-PLME_SAP (1470).

WSM element of one example of the present invention can be transmittedby the sequential procedures of MAC (1410) and PHY (1420). Also, WSMelement of one example of the present invention can be received by thesequential procedures of PHY (1420) and MAC (1410).

Although the embodiments of the present invention have been disclosed inview of each aspect of the invention, those skilled in the art willappreciate that embodiments of each aspect of the invention can beincorporated. And, there can be advantages not explicitly discussed,since they are obvious from the description for those skilled in theart.

What is claimed is:
 1. A method of scanning existing networks at a firststation in a communication system, the method comprising: receiving, bya first station, a white space map (WSM) comprising information foravailable channels from a second station; and scanning, by the firststation, the existing networks on the available channels identifiedwithin the received WSM, wherein scanning the existing networks isperformed by one or more of a first scheme or a second scheme, the firstscheme comprising listening to a beacon frame from an AP station of abasic service set (BSS) on a specific channel among the availablechannels identified by the received WSM, the second scheme comprisingtransmitting a probe request frame to an AP station of the BSS on anychannel among the available channels identified by the received WSM; andreceiving a probe response frame in response to the probe request frame.2. The method of claim 1, wherein the probe request frame is nottransmitted on a channel other than the available channels identified bythe received WSM.
 3. The method of claim 1, wherein: the first stationis a dependent station, and the second station is an enabling station;and the dependent station is a station receiving the information for theavailable channels from the enabling station that enables the operationof the dependent station.
 4. The method of claim 1, wherein the firststation operates only within the available channels identified by theWSM.
 5. The method of claim 1, wherein the WSM is received via one of: abeacon frame, a probe response frame, and a white space map announcementframe.
 6. The method of claim 1, further comprising: receiving, at thefirst station, an updated WSM from the second station, wherein the firststation scans the existing networks on the available channels identifiedwithin the updated WSM.
 7. An apparatus for scanning existing networksin a communication system as a first station, the apparatus comprising:a transceiver configured to receive a white space map (WSM) comprisinginformation for available channels from a second station; and aprocessor configured to: control scanning the existing networks on theavailable channels identified within the received WSM; control thetransceiver to perform the scanning by one or more of a first scheme ora second scheme; control the transceiver to listen to a beacon framefrom an AP station of a basic service set (BSS) on a specific channelamong the available channels identified by the received WSM according tothe first scheme; control the transceiver to: transmit a probe requestframe to an AP station of the BSS on any channel among the availablechannels identified by the received WSM; and receive a probe responseframe in response to the probe request frame according to the secondscheme.
 8. The apparatus of claim 7, wherein the processor controls thetransceiver not to transmit the probe request frame on a channel otherthan the available channels identified by the received WSM.
 9. Theapparatus of claim 7, wherein: the apparatus is configured to operate asa dependent station; the second station is an enabling station; and thedependent station is a station receiving the information for theavailable channels from the enabling station that enables the operationof the dependent station.
 10. The apparatus of claim 7, wherein theprocessor is configured to control the apparatus to operate only withinthe available channels identified by the WSM.
 11. The apparatus of claim7, wherein the WSM is received via one of: a beacon frame, a proberesponse frame, and a white space map announcement frame.
 12. Theapparatus of claim 7, wherein the processor is further configured toscan the existing networks on the available channels identified withinan updated WSM, when the transceiver receives the updated WSM from thesecond station.